“21 Jump Street” might have seemed like your typical R-rated comedy — the “Bridesmaids”-y debut at SXSW, the Apatow-infused cast — but beyond the obvious, the TV reboot featured one big surprise for ticket buyers this weekend: Johnny Depp. Yes, that Johnny Depp, one of the five biggest stars on the planet, shared jokes and bullets with Jonah Hill and Channing Tatum, as well as original Jump Streeters Peter DeLuise and Holly Robinson Peete, in the new comedy. So! How did Depp end up in “21 Jump Street,” and whose idea was it to use him in a way that recalled Bill Murray’s cameo “Zombieland”?

“Jonah wanted to approach Johnny Depp very early in the process,” screenwriter Michael Bacall (“Scott Pilgrim vs. The World”) told Moviefone before the film’s release. “It took a while, but we kinda heard through the grapevine that he might be interested in it.”

He was, but with a caveat: Depp wanted his “21 Jump Street” character to have some “closure,” as Bacall said, in a way that would wrap up his ’80s storyline.

“It is such a funny idea,” Bacall said with a laugh. “Huge credit to him for having that idea. Then we just immediately took that ball and ran with it, and wanted to take it as far as we could.”

Bacall and Hill (who has a story credit on the film) made good on their word, giving Depp a “21 Jump Street” send-off worthy of “True Romance.” And while Depp’s appearance in the film is fairly brief, the star made an immediate impact on set.

“That was our third day on the set,” co-director Phil Lord told Moviefone last week. “Basically, on a movie set that we were supposed to be in charge, you realize how not in charge of anything you are. How crazy that can make a set. And then you realize instantly why someone like that is such a big movie star. He walks on set, there’s no smoking on set. ‘OK, no problem.’ He’s smoking. You’re like, ‘Of course!’ That’s what makes him awesome.”

Despite shrugging off the no-smoking rules, Lord said Depp was a great collaborator. “Such a creative guy. Such a genuine person, great improviser. Game. Doesn’t take himself so seriously. It was like, ‘I understand why he makes a kajillion dollars.’ He’s awesome. Everything you would hope for in a movie star, he’s it.”

Judging from how things end up, it’s doubtful Depp will return for any sequel to “21 Jump Street.” Bacall said that he’s got some ideas for a second part already, however — and with $ 35 million in ticket sales over the weekend, it seems likely he’ll have the chance to put them into action.

Superstar Brad Pitt obviously doesn’t take himself TOO SERIOUSLY as an actor. Because radio detection and rangingOnline.com can exclusively reveal that the 50-year-old filmed a hilarious cameo playing ...